Page 26 |
Save page Remove page | Previous | 26 of 209 | Next |
|
small (250x250 max)
medium (500x500 max)
Large (1000x1000 max)
Extra Large
large ( > 500x500)
Full Resolution
All (PDF)
|
This page
All
|
that have features interpreted as indicative of large and sudden movements involving
thousands of cubic kms of the lower continental slope. The presence of these large
offshore submarine landslides suggests a mechanism for generating anomalously large
tsunamis at infrequent intervals.
The PG&E (2003) report provides an overview of tsunami modeling efforts per-formed
for this region. Based on empirical data alone, it suggested that a tsunami-genic
earthquake of magnitude 8.8 on the Cascadia subduction zone would generate
runup heights along the northern California coast of 9.5m. The runup range empiri-cally
inferred for Mw 8.5 to 9.2 events is 8 − 11m, in general agreement with estimates
of 9 − 12m for waveheights offshore Humboldt Bay, estimated based on paleotsunami
studies in northern California.
1.1.6 Earlier work on Tsunami Hazards in San Francisco Bay
Several previous studies have looked at inundation, tsunami heights, and estimated
recurrence for San Francisco Bay. Ritter and Dupre (1972) mapped areas of potential
tsunami inundation within the bay (Figure 1.2). They assumed only teletsunami sources
and used a waveheight of 6.1m at the Golden Gate. This value was chosen because
it was the approximate value of peak inundation at Crescent City in 1964. They used
Magoon’s (1966) attenuation relation to estimate heights of possible flooding through-out
the bay. For example, the peak amplitude at Oakland was found as 3m, and at Mare
Island as 0.6m. They extrapolated Wiegel’s (1970) frequency of occurrence graph for
San Francisco Bay to estimate that the mapped inundation (Figure 1.2) represented a
200–year event. Wiegels frequency graph was based primarily on five events (1946,
11
Object Description
| Title | Deterministic and probabilistic tsunami studies in California from near and farfield sources |
| Author | Uslu, Burak |
| Author email | uslu@usc.edu; burak.uslu@noaa.gov |
| Degree | Doctor of Philosophy |
| Document type | Dissertation |
| Degree program | Civil Engineering |
| School | Viterbi School of Engineering |
| Date defended/completed | 2007-09-21 |
| Date submitted | 2008 |
| Restricted until | Unrestricted |
| Date published | 2008-10-30 |
| Advisor (committee chair) | Synolakis, Costas E. |
| Advisor (committee member) |
Bardet, Jean-Pierre Okal, Emile A. Moore, James Elliott, II |
| Abstract | California is vulnerable to tsunamis from both local and distant sources. While there is an overall awareness of the threat, tsunamis are infrequent events and few communities have a good understanding of vulnerability. To quantitatively evaluate the tsunami hazard in the State, deterministic and probabilistic methods are used to compute inundation and runup heights in selected population centers along the coast.; For the numerical modeling of tsunamis, a two dimensional finite difference propagation and runup model is used. All known near and farfield sources of relevance to California are considered. For the farfield hazard analysis, the Pacific Rim is subdivided into small segments where unit ruptures are assumed, then the transpacific propagations are calculated. The historical records from the 1952 Kamchatka, 1960 Great Chile, 1964 Great Alaska, and 1994 and 2006 Kuril Islands earthquakes are compared to modeled results. A sensitivity analysis is performed on each subduction zone segment to determine the relative effect of the source location on wave heights off the California Coast.; Here, both time-dependent and time-independent methods are used to assess the tsunami risk. In the latter, slip rates are obtained from GPS measurements of the tectonic motions and then used as a basis to estimate the return period of possible earthquakes. The return periods of tsunamis resulting from these events are combined with computed waveheight estimates to provide a total probability of exceedance of given waveheights for ports and harbors in California. The time independent method follows the practice of past studies that have used Gutenberg and Richter type relationships to assign probabilities to specific tsunami sources.; The Cascadia Subduction Zone is the biggest nearfield earthquake source and is capable of producing mega-thrust earthquake ruptures between the Gorda and North American plates and may cause extensive damage north of Cape Mendocino, to Seattle. The present analysis suggests that San Francisco Bay and Central California are most sensitive to tsunamis originating from the Alaska and Aleutians Subduction Zone (AASZ). An earthquake with a magnitude comparable to the 1964 Great Alaska Earthquake on central AASZ could result in twice the wave height as experienced in San Francisco Bay in 1964.; The probabilistic approach shows that Central California and San Francisco Bay have more frequent tsunamis from the AASZ, while Southern California can be impacted from tsunamis generated on Chile and Central American Subduction Zone as well as the AASZ. |
| Keyword | assessment; California; hazard; model; probability; tsunami |
| Geographic subject | capes: Kamchatka; islands: Kuril Islands; fault zones: Cascadia Subduction Zone |
| Geographic subject (state) | California; Alaska |
| Geographic subject (country) | Chile |
| Coverage date | 1952/2008 |
| Language | English |
| Part of collection | University of Southern California dissertations and theses |
| Publisher (of the original version) | University of Southern California |
| Place of publication (of the original version) | Los Angeles, California |
| Publisher (of the digital version) | University of Southern California. Libraries |
| Provenance | Electronically uploaded by the author |
| Type | texts |
| Legacy record ID | usctheses-m1706 |
| Contributing entity | University of Southern California |
| Rights | Uslu, Burak |
| Repository name | Libraries, University of Southern California |
| Repository address | Los Angeles, California |
| Repository email | cisadmin@lib.usc.edu |
| Filename | etd-uslu-2434 |
| Archival file | uscthesesreloadpub_Volume40/etd-uslu-2434.pdf |
Description
| Title | Page 26 |
| Contributing entity | University of Southern California |
| Repository email | cisadmin@lib.usc.edu |
| Full text | that have features interpreted as indicative of large and sudden movements involving thousands of cubic kms of the lower continental slope. The presence of these large offshore submarine landslides suggests a mechanism for generating anomalously large tsunamis at infrequent intervals. The PG&E (2003) report provides an overview of tsunami modeling efforts per-formed for this region. Based on empirical data alone, it suggested that a tsunami-genic earthquake of magnitude 8.8 on the Cascadia subduction zone would generate runup heights along the northern California coast of 9.5m. The runup range empiri-cally inferred for Mw 8.5 to 9.2 events is 8 − 11m, in general agreement with estimates of 9 − 12m for waveheights offshore Humboldt Bay, estimated based on paleotsunami studies in northern California. 1.1.6 Earlier work on Tsunami Hazards in San Francisco Bay Several previous studies have looked at inundation, tsunami heights, and estimated recurrence for San Francisco Bay. Ritter and Dupre (1972) mapped areas of potential tsunami inundation within the bay (Figure 1.2). They assumed only teletsunami sources and used a waveheight of 6.1m at the Golden Gate. This value was chosen because it was the approximate value of peak inundation at Crescent City in 1964. They used Magoon’s (1966) attenuation relation to estimate heights of possible flooding through-out the bay. For example, the peak amplitude at Oakland was found as 3m, and at Mare Island as 0.6m. They extrapolated Wiegel’s (1970) frequency of occurrence graph for San Francisco Bay to estimate that the mapped inundation (Figure 1.2) represented a 200–year event. Wiegels frequency graph was based primarily on five events (1946, 11 |
